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And it's a nifty sound. Amp sounds hotter, cluckier, chimier, (are those words? "more chimey", haha) livelier. The interaction with the speaker is quite interesting, it's like playing a valvestate amp with the "tube dynamics" button off, then that change in tone you hear with it on, removing NFB in my amp is not unlike hitting that button.
I recommend it as it's such an easy mod with a drastic effect on the sound of the whole amp, and a rather musical one. I just clipped the NFB wire for now but I will eventually wire it to a switch when I figure out the best way to install a switch. Maybe in the extension speaker hole, which I never use. Would like to leave the amp looking as stock as possible in case I ditch it one day lol
Can I do a on-off-on SPDT toggle switch wired like this? I havent had my coffee yet, this will give
me half feedback/no fb/stock fb?
original nfb wire to 820Ω R
nfb Wire from speaker jack
680Ω R to original nfb wire for 1.5KΩ
FWIW I also tried my JJ 6v6s biased as hot as my amp would allow, (29.3 mA @ 413V) and severed the power supply to pin 4 of the 6v6 and tied pin 4 to pin 3. The result was mixed, the amp was certainly quieter (lower noise floor), and bright but not as rich for sure. The bass was really saggy, almost like a very smooth clipping going on with just the bass freqs, kinda blurring and creaming out the attack. Could be useful for low volume clean recording. In stock form, the amp has a little hiss that no one on stage would care about but at idle you can certainly hear that it's on. In triode mode the hiss was almost totally gone. Anyways it's as "vintage" of a sound as I've heard from jj 6v6s, they normally sound to me very big and have a weird midrange but this made them warmer and softer. Maybe too much though.
I'll be looking for ways to reduce the noise floor without triode mode cuz I don't feel that's worth leaving that way or putting on a switch.
As far as noise floor I want to do metal film plate resistor on v1a and b as it's the first stages of both channels and the post tone stack of the vintage channel, and higher wattage carbon comp resistors on v2 a and b where I'm pretty sure theres most of the preamp gain happening, and higher wattage carbon comps on the PI tail and load resitors for mojo.
V4a is the reverb recovery stage and on silverface deluxes to reduce reverb noise they put a small bypass cap on the 220k grid leak to get rid of reverb hiss. Most of my amps noise is when the reverb is up.
Reallllly wanna do these mods but nervous about working on the crowded PCB. Plus I have to go source all this crap anyways.
Anyways thoughts/comments?
I recommend it as it's such an easy mod with a drastic effect on the sound of the whole amp, and a rather musical one. I just clipped the NFB wire for now but I will eventually wire it to a switch when I figure out the best way to install a switch. Maybe in the extension speaker hole, which I never use. Would like to leave the amp looking as stock as possible in case I ditch it one day lol
Can I do a on-off-on SPDT toggle switch wired like this? I havent had my coffee yet, this will give
me half feedback/no fb/stock fb?
original nfb wire to 820Ω R
nfb Wire from speaker jack
680Ω R to original nfb wire for 1.5KΩ
FWIW I also tried my JJ 6v6s biased as hot as my amp would allow, (29.3 mA @ 413V) and severed the power supply to pin 4 of the 6v6 and tied pin 4 to pin 3. The result was mixed, the amp was certainly quieter (lower noise floor), and bright but not as rich for sure. The bass was really saggy, almost like a very smooth clipping going on with just the bass freqs, kinda blurring and creaming out the attack. Could be useful for low volume clean recording. In stock form, the amp has a little hiss that no one on stage would care about but at idle you can certainly hear that it's on. In triode mode the hiss was almost totally gone. Anyways it's as "vintage" of a sound as I've heard from jj 6v6s, they normally sound to me very big and have a weird midrange but this made them warmer and softer. Maybe too much though.
I'll be looking for ways to reduce the noise floor without triode mode cuz I don't feel that's worth leaving that way or putting on a switch.
As far as noise floor I want to do metal film plate resistor on v1a and b as it's the first stages of both channels and the post tone stack of the vintage channel, and higher wattage carbon comp resistors on v2 a and b where I'm pretty sure theres most of the preamp gain happening, and higher wattage carbon comps on the PI tail and load resitors for mojo.
V4a is the reverb recovery stage and on silverface deluxes to reduce reverb noise they put a small bypass cap on the 220k grid leak to get rid of reverb hiss. Most of my amps noise is when the reverb is up.
Reallllly wanna do these mods but nervous about working on the crowded PCB. Plus I have to go source all this crap anyways.
Anyways thoughts/comments?
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